Mavis Wanczyk, a medical worker from Massachusetts, whose ex-husband was killed by a hit-and-run driver last year, was revealed as the winner of the largest single Powerball prize in the country's history during a Thursday press conference.

Wanczyk, 53, bought the winning $2 ticket at a Pride gas station store in Chicopee, Mass., around 2:30 p.m. Wednesday as fever over the prize was growing.

A lump-sum cash value, before taxes, would be $443 million, lottery officials said.

The happy turn comes after tragedy struck Wanczyk's family in November — her ex-husband, William Wanczyk, a former firefighter, was killed in a hit-and-run crash in November, according to Mass Live.

Peter Sheremeta, a 20-year-old who prosecutors say was drunk when he drove into a bus shelter, was arrested in June on charges including manslaughter and motor vehicle homicide.

Mavis Wanczyk of Massachusetts was revealed as the winner of the $758 million Powerball jackpot. (Josh Reynolds/AP)

Wanczyk said she was walking out of work at a medical center late Wednesday when a firefighter friend named Rob told her the winning numbers — and shared in her life-changing discovery.

He predicted the winner was a ticket buyer who chose birthday numbers.

"Oh, yeah, I know, it's never going to be me," she responded. "It's just a pipe dream I had."

She couldn't believe her ticket matched all six numbers.

"I couldn't drive anywhere and I couldn't do anything," she told reporters as she stood smiling in front of a giant check.

He firefighter friend followed her home to make sure she arrived safely.

The winning ticket was sold at a Pride gas station in Chicopee, Mass. (REUTERS/Brian Snyder)

On Wednesday, the mother of two bought two Quick Picks and used "basically random" numbers for the third ticket.

The winning numbers included birthdays and the number 4, based on the size of a group of relatives and friends who dine together on Friday nights.

"I just happened to choose and it worked to my advantage," she said. "It really did."